The present invention is directed to a socket having gripping means for gripping a tool having a cylindrical shaft, such as a dental tool. The socket includes a sleeve-shaped shaft which is mounted for rotation and accepts a clamping sleeve which holds a tool shaft. The clamping sleeve has at least two longitudinal slots extending inward from a first end of the clamping sleeve which faces away from the tool to form resilient tongues which are movable from a clamping position for engaging the tool shaft to an outward position to allow releasing of the shaft. The socket includes an axially movable ram, which is actuated by a handle for the purpose of moving the tongues from the clamping position to an unclamped position to allow releasing the tool, and the ram has an outside tapering conical surface for engaging the one end of the clamping sleeve which is provided with an inwardly tapering surface.
A rotary socket having a clamping sleeve for gripping a shaft of a tool is disclosed in U.S. Pat. No. 4,089,115. In this arrangement, a ram is threaded into the end of the shaft and is movable by means of a separate tool, such as a polygonal-shaped wrench or the like, from a retracted position withdrawn from engagement with the gripping sleeve to a position causing the gripping sleeve to release the tool. In the clamped position, the tool shaft is held by the clamping tongues of the clamping sleeve with a fricational grip. In a retracted position, the ram is situated at a slight axial distance from the corresponding ends of the sleeve. For removing the tool, the ram is threaded into the shaft until its outside conical end engages inside, conical surfaces of the clamping sleeve to resiliently bias the tongues radially outward to a releasing position to release the tool shaft.
Dependent on the extent on which the ram is screwed into the shaft, a certain pre-adjustment of the clamping tongues can also be achieved with this device. The two cones are in engagement with one another in this pre-adjustment on one hand, but on the other hand, a reliable holding of the tool shaft in the clamped position still is established.
A disadvantage with this clamping device is that an additional tool is required for removing a tool that is gripped in the gripping sleeve. Another significant disadvantage, moreover, is that the clamping tongues are subjected to a torsional stress when the ram is screwed in and, thus, the useful life of the clamping sleeve is reduced.
Another known type of clamping device or socket is disclosed in German OS 34 02 635. As disclosed, a pre-adjustment of the clamping tongues, such as mentioned above, is achieved in that the clamping tongues are spread by a pressure member, which is seated in an axial movable fusion in the head housing. A stop element for one-time adjustment of this pre-adjustment is allocated to this pressure member, and this stop element is positioned in various positions by means of being screwed into the shaft and limiting the movement of the pressure member from the clamping sleeve. Of the two exemplary embodiments shown in this German reference, one, likewise, has the disadvantage that relatively high forces must be exerted in order to bring the clamping sleeve out of the clamping position into an unclamped position to allow removal of the tool. The other embodiment is relatively complicated to manufacture due to the many parts of the arrangement composed of the spreader element and pressure member and, in particular, due to the spreader element with the key surfaces. Another disadvantage is that the spreader element must be integrated positionally dependent on the clamping sleeve and this makes assembly more difficult.